L. David Roper
This article compares the effective price of "fuel" for regular-gasoline (gallons of gasoline) cars and electric (kWh of electricity) cars. The assumption is made that gasoline cars are ~25% efficient in converting regular gasoline in the car's tank to motive energy and electric cars are ~90% efficient in converting electric energy in the car's battery to motive energy. An efficiency ratio is defined as eff. = 90/25 = 3.6 .
The data for average yearly prices of regular-gasoline prices and electricity rates are calculated from monthly data given in http://data.bls.gov/cgi-bin/surveymost?ap . The energy (kWh) in a gallon of gasoline is taken as 36.6 kWh/gallon.
The next two graphs compare the two fuel types for cars in $/gallon and in $/kWh:
The ratio of regular-gasoline effective price to electricity effective price for electric cars is:
The trend for the last decade is that fuel for gasoline cars is rising much more rapidly than fuel for electric cars.
Comparison of global-warming emissions and fuel-cost savings across the United States